Hi,
Just a quick note about the DR-680 firmware upgrade V1.20 (note, this is the very new release, not the earlier V1.12). So far, the only information I've been able to find is in Japanese, but I've downloaded and installed the firmware form the Tascam Japan site and in addition to the M/S functions, the DR-680 now has ganging functions available for gain, pan and trim, including the possibility of separate ganging for groups of inputs. For example, I record in A & B-Format and M/S at the same time and I can gang inputs 1-4 for the ambisonic inputs and 5-6 separately for the M/S inputs. You just push all the channel select buttons that you want to gang at the same time and once again to de-select. Very simple.
Regards,
John